Planning With Plants in Illinois

Kenneth R. Robertson
Center for Biodiversity
Illinois Natural History Survey
607 East Peabody Drive

Originalliy published in: James B. Phipps and Paul M. Catling, editors. 2001. Bioconservation and Systematics. Proceedings of the Canadian Botanical Association Conference Symposium in London, Ontario, June 2000. Published by the Canadian Botanical Association. ISBN 0-9689565-0-5.


Illinois is an ecologically diverse state, and probably more is known about its vegetation than of any other state. Yet, most of the natural landscape has been destroyed by agriculture and urban expansion. Because Illinois has so little nature left, it has become a leader in the area of the preservation and protection of remnants of the natural ecosystems. In this paper, a summary is presented of a series of interrelated programs that became powerful tools in the preservation of natural areas. Also described is a recent program designed to monitor long-term ecological trends in the state.

When the first European settlers arrived in what is now Illinois, they saw a wealth of natural diversity in the landscape. Studies of the natural resources of Illinois began soon after it gained statehood in 1818. Over the past 180 years the efforts of botanists, zoologists, geologists, and other scientists have resulted in a vast accumulated knowledge; probably more information is available about the natural resources of Illinois than just about anyplace else on earth (Jeffords 2000). This knowledge is contained in both a voluminous published literature as well as in natural history collections.

Risser’s (1984) extensive bibliography lists 1277 publications on the vegetation of Illinois. The earliest paper on Illinois was evidently by Van Zandt (1818) on what is today Calhoun County. The first published "Flora" of Illinois was by Lapham (1857). Over the years, a number of significant state-wide floras have been published, including Jones (1963) and Mohlenbrock (1967, 1986). Dot map distributions of vascular plant species by county have been published by Jones and Fuller (1955), Winterringer and Evers (1960), and Mohlenbrock and Ladd (1978). There are about 2,068 species of vascular plants native to Illinois (Post 1991). Only three species are endemic to Illinois, Iliamna remota (Malvaceae), Boltonia decurrens (Asteraceae), and Thismia americana (Burmanniaceae); the last is presumed to be extinct.

Over the past 150 years most of the landscape of Illinois has been converted to agriculture and urban areas. As a result, less than 1% of the original landscape is still extant, and Illinois now ranks near the bottom of the 50 states in this respect. Perhaps because so much of our natural heritage has been lost, Illinois has become a leader in the movement to inventory, protect, manage, and study what is left. In this paper, I will concentrate on some important developments and projects that have occurred in the past 40 years that have had, and continue to have, a profound effect on plants and the vegetation of Illinois.


The state of Illinois is situated rather centrally in the North American continent. Illinois is a long state from north to south, a distance of about 612 km ( 380 miles). The northern border is about 42° 30' N, nearly the same latitude as Boston, Massachusetts, while the southern border is about 37° 00' N, almost the same as Norfolk, Virginia. The state lies between about 87° 30' W and 91° 30' W longitude, a distance of about 346 km (215 miles).

Much of the boundary of Illinois is determined by bodies of water. The entire western border of Illinois is formed by the Mississippi River, Lake Michigan forms the border in the northeastern part of the state, and the southern and southeastern border are the Ohio and Wabash rivers. There is not a great deal of altitudinal range in Illinois, the highest point being Charles Mound in the northwestern part of the state at 376 meters (1,235 feet), while the lowest point is 85 meters (279 feet) at the southern boundary of the state at the confluence of the Mississippi and Ohio rivers.

Four glacial advances occurred over what is now Illinois: the Nebraskan, Kansan, Illinoian, and Wisconsinan glacial epochs (Willman and Frye 1970, Pielou 1991). However, only the last two strongly influenced the landforms extant today. The southernmost advance of the Illinoian was to within 80 km (50 miles) of the southern tip of Illinois, just north of what are now known as the Shawnee Hills; this was the southernmost extent of the Pleistocene glaciations. Wisconsinan glaciation covered about the northeastern one-half to two-thirds of Illinois; it receded slowly 20,000 to 10,000 years ago. Only extreme northwestern Illinois (the "Driftless" area) and southern Illinois, plus a few other small areas, escaped glaciation. Glaciation has had a profound impact on the Illinois landscape. The central part of the state is extremely flat, with moraines forming the only topographical relief. Moraines are more abundant around the Chicago area, and the terrain is more rolling in western Illinois. Rugged hills can be found in the mostly unglaciated regions of extreme northwestern Illinois, southern Illinois, and along parts of the Mississippi and Illinois rivers.

As a result of the large latitudinal range and the geological diversity, Illinois has a wide variety of natural ecological communities. At the time of European settlement, about 40% of Illinois was in forest, while 60% was in prairie (Anderson 1970). Prior to European settlement, the vegetation of much of the Midwest was a shifting mosaic of prairie, forest, savanna, and wetlands that was largely controlled by the frequency of fire under climatic conditions that were capable of supporting any of these vegetation types. Sand dunes, beaches, bogs, fens, sedge meadows, marshes, forests, savannas, and a wide variety of prairies could be found in northern Illinois. Along the Mississippi and Illinois rivers loomed tall cliffs, often capped by hill prairies, with the bottomlands and uplands covered in dense forests. A vast sea of tallgrass prairie occupied central Illinois, with isolated wooded groves standing like islands. Southern Illinois had stately bald cypress and tupelo swamps, hardwood forests containing large trees, prairie-like glades, and canyons with cliffs of limestone and sandstone (Jeffords, Post, and Robertson 1995; Robertson, Anderson, and Schwartz 1997).



The Illinois Nature Preserves Commission

The year 1963 is pivotal because it is when the Illinois Nature Preserve Commission (INPC) was established. This was largely due to the efforts of a single individual, George B. Fell (1916—1994). George Fell’s father was Egbert W. Fell, who intensively studied the flora of Winnebago County for many years, resulting in the publication of a flora (Fell 1955). George Fell accompanied his father on many field trips. Eventually, he noticed "the remnants of the natural vegetation being destroyed one by one." In 1948, George Fell went to Washington, DC as vice-president of the Ecologists Union with the charge to open an office there for the organization. In 1950, the name was changed to The Nature Conservancy (Fell 1983). Fell was the first executive director of that organization, a title he held from 1953 until 1958 (Allen 1993). In fact, he was first and only employee of TNC during its critical formative years and "helped frame the guiding principles of The Nature Conservancy, principles that continue to this day" (Sawhill 1994). Fell was also instrumental in founding the Natural Areas Association.

George Fell was perhaps better at planting acorns and watching the oaks grow than nurturing the oaks to full maturity (an analogy from Allen 1993). In 1958 he left TNC and returned to Illinois and founded The Natural Land Institute in Rockford to coordinate the efforts of natural area organizations, volunteers, and governmental agencies. In 1961 he was instrumental in drafting legislation that would establish a system of nature preserves in Illinois. It took another two years, but in 1963 the bill was passed by the legislature and signed by the governor, and the Illinois Nature Preserves Commission was established. The Natural Land Institute served as the operating agent for INPC, with George Fell as the executive secretary from 1964 until 1982.

The INPC legislation established a nine member commission appointed by the governor, in consultation with the heads of the Illinois State Museum and the Illinois Natural History Survey. The commission was empowered to officially dedicate nature preserves that are legally protected in perpetuity, and dedicated nature preserves may not be condemned for another use; the legal protection is the strongest protection for land in Illinois. Official nature preserves may be either publicly or privately owned. From its inception, the INPC has worked closely with the Illinois Department of Conservation and its successor the Illinois Department of Natural Resources. The INPC has a small staff and does not own nature preserves itself.

In the first 10 years of its existence, the INPC dedicated abut 50 nature preserves, and by the end of 1999 this had grown to 296 preserves (Figure 2) protecting 15,800 hectares (39,040 acres). The Illinois Department of Natural Resources is the largest landowner, but many preserves are owned by county forest preserve or conservation districts, municipalities, The Nature Conservancy, conservation organizations, corporations, and private individuals (McFall and Karnes 1995; Illinois Nature Preserves Commission 1999).

The establishment of INPC soon led to a number of other activities. The INPC legislation set a major goal to preserve adequate examples of all significant natural features found in Illinois. This created the need to know exactly what natural features did in fact occur in the state.

The Natural Divisions of Illinois

There had been several attempts to devise a classification system for the biological landscape in Illinois (Telford 1926, Vestal 1931, Smith 1961, Iffrig and Bowles 1983). The INPC saw a need to develop a modern classification system that would serve as a framework for identifying significant natural features that should be included in the preserve system and to help set priorities for land acquisitions and for establishing preserves. This resulted in the Natural Divisions of Illinois or NDI (Schwegman 1973); partially reprinted in Mohlenbrock (1986). The concept behind natural divisions is that they "are geographic regions of a larger entity like a state or continent. A division contains similar landscapes, climates, and substrate features like bedrock and soils that support similar vegetation and wildlife over the division’s area. Natural divisions help conservationists classify land for purposes like protecting natural diversity" (Schwegman 1997).

In the classification scheme that resulted, 15 Natural Divisions were delimited in Illinois, with most of the divisions subdivided into sections, resulting in a total of 34 units (Figure 1). Factors taken into consideration included topography, soils, bedrock, glacial history, and the distributions of plants and animals. The publication included a map as well as text describing the main features of each of the divisions and sections. Seven major categories of terrestrial plant communities were used in the publication: forest, prairie, fen, marsh, sedge meadow, and bog.

The Illinois Natural Areas Inventory

Implicit in the goals of the INPC is the aim to protect "high quality" examples of the natural features found in the state. In order to effectively do this, and to help set priorities for acquisition and preservation, the following were needed: a detailed classification system of natural biotic communities, a system to rate the quality of natural communities, and information on individual natural remnants, such as location, size, and quality.

These were the objectives of the Illinois Natural Areas Inventory (INAI), a major project conducted during the mid-1970s with funding provided by the Illinois Department of Conservation. The scale of the INAI was unprecedented at the time as it was the first state-wide inventory in the United States; the total cost exceeded $600,000, and more than 200 staff and volunteers participated in the project. The methodologies and results of the initial INAI are presented in White (1978; also see White 1981a, b, c) and White and Madany (1978). Three principal results of the INAI are discussed here: natural community classification system, grading the quality of natural areas, and the inventory itself.

The numerous systems that have been used to classify vegetation basically fall into two broad approaches: physiognomy and floristic composition (Harty, 1981). Physiognomic classifications are based on categories, such as forest, savanna, grassland, bog, etc. An example of a physiognomic system is that developed by Kuchler (1964) and widely used in the U. S. Forest Service. The second approach, floristic composition, is exemplified by the Braun-Blanquet system (Whittaker (1973). According to Whittaker (1973), a desirable goal would be to "marry" the two approaches into a single classification system, where floristic units would be combined by their structure into physiognomic units.

The classification system developed by the INAI has two components (White and Madany 1978, Harty 1981). The first system is the landscape scale Natural Divisions of Illinois, as outlined above. Then the INAI combined the physiognomic and floristic approaches by defining community classes by physiognomic features (forest, prairie, etc.) and natural communities generally on soil type and soil moisture gradients (floodplain forest, dry sand prairie), and then gave short lists of dominant plant species and characteristic plant and animal species for each natural community (Harty 1981). The resulting natural community classification system recognized nine community classes, with each class further subdivided into natural communities (Table 1). There were then various combinations of the different community classes and natural communities with the different natural divisions and sections.

The second major result of the INAI was the development of a scheme for rating the quality of individual remnants of natural communities. This grading system provides terms for describing the relative amount of successional instability or change in a community’s natural diversity, species composition, and structure due to disturbances. Basic guidelines developed by the INAI (White1978, 1981b) are listed in Table 2. There are five grade categories, based primarily on the degree of artificial or natural disturbances. Grade A natural communities are relatively stable or undisturbed while Grade E communities have been severely disturbed; the other grades represent intermediate stages.

The third major outcome of the INAI was the actual inventory of sites. In order to be included on the Inventory, a natural area must have at least one significant feature. The following are the seven categories of significant features: high quality terrestrial or wetland natural community, habitats with endangered species, habitats with relict species, outstanding geologic features, lands that are managed and used for natural science studies, unique natural features, and outstanding aquatic features. When considering the first category, high quality natural communities, "high quality" refers only Grades A and B in the rating system. Most types of natural communities had to be at least 20 acres (8.1 hectares) in size, except for communities that are normally small, such as seeps, and for communities that are extremely rare today, such prairies, which could be as small as 0.25 acre (0.1 hectare) (McClain 2000).

At the time the INAI was initially completed in the late 1970s, a total of 1,089 sites were included, covering 10,410 hectares (25,723 acres) (White 1978). This represents only 0.07% of all the land area of Illinois. A total of 99 of the 102 counties in Illinois had at least one site, but areas were concentrated in the extreme ends of the state, with 573 areas in the northern 2 tiers of counties and 396 in the southern 3 tiers of counties; there were also numerous areas along the Illinois and Mississippi rivers (see Figure 3). The resulting data was sorted in a variety of ways. For instance, a total of 25,723 acres of Grades A and B natural communities were identified (Table 3). Another tabulation listed acreages by natural community and by natural division; see the example in Table 4. Much information from the INAI was entered into a computer and stored on floppy disks on a small desktop computer (McClain 2000). Today, the inventory data are part of the Illinois Natural Heritage Database.

The registry of areas included on the INAI has been kept up-to-date. Unfortunately, some areas have been destroyed, while additional fieldwork has identified new areas worthy of being included on the Inventory. There are now a series of guidelines for placing new areas on the Inventory. As of August 2000, there were 1,193 sites on the Inventory (Figure 3) that encompass143,409 hectares (354,358 acres).

Endangered Species Protection Board

Legal responsibility for endangered and threatened species in Illinois rests with the Illinois Endangered Species Protection Board. The Illinois Endangered Species Protection Act was passed by the legislature in 1972. It originally only protected animal species; some coverage was given to plants in 1977, but they were not given full protection until 1985 (Herkert 1991).

During the late 1970s, the Endangered Species Project was undertaken to determine the status of major groups of Illinois organisms through literature review, examinations of specimens in museums and herbaria, and workshops with specialists. This resulted in the first official lists of endangered and threatened species of the state, which included only vertebrate animals and vascular plants (Bowles, Diersing, and Ebinger 1981). These lists have subsequently been officially revised in 1989, 1990, 1994, and 1999. The list now includes invertebrates (snails, mussels, crustaceans, and insects). Currently, 265 taxa of plants are listed as State Endangered and 66 taxa as Threatened; only 8 of these are listed at the Federal level. Most Endangered and Threatened plants occur in Illinois at the edge of their geographical ranges or are rare throughout their ranges.

Division of Natural Heritage

The missing link was a governmental unit whose responsibility was to implement policy and programs to inventory, protect, and manage natural areas and endangered species habitats. Consequently, constituency groups interested in protecting Illinois’ natural heritage lobbied to create a unit within state government to work specifically on natural heritage issues. The result was the creation of the Division of Natural Heritage within the Illinois Department of Conservation (now Department of Natural Resources).

As a result of the Illinois Nature Preserves Commission, the Natural Divisions of Illinois, the Illinois Natural Areas Inventory, the Endangered Species Protection Board, and the creation of the Division of Natural Heritage, Illinois had in place a powerful set of political and scientific tools to preserve natural areas in the state by the late 1970s. The legal means were in place to permanently protect natural areas through dedication as an Illinois Nature Preserve. Species could be officially listed as endangered or threatened. The state was divided into a series of logical natural divisions, there was a detailed classification system for the natural communities, and an inventory had been done to identify examples of high quality remnants of each natural community still extant in each natural division.

With all this information, the INPC and Division of Natural Heritage developed the Illinois Natural Areas Plan (Illinois Department of Conservation 1980). It was this complete package that gave credibility to preservation efforts. Administrators and managers might not understand the biological significance of preserving natural areas, but they could more readily understand the justifications for preservation given in the following examples.

"…the Illinois Natural Areas Inventory found that only 6.3 acres of high-quality mesic prairie remain in the Western Forest-Prairie Natural Division of Illinois. Dedication of Brownlee Cemetery Prairie would help ensure representation of a type of vegetation that dominated the original landscape of Illinois" (Meyer 1982).

"Dry-mesic sand savanna is found in areas of intermediate elevation. One hundred ninety acres of a total 272 acres of dry-mesic sand savanna are Grade B.…The 190 acres represent approximately 41% of the total 459 acres of high quality dry-mesic sand savanna in the Kankakee Sand Area Natural Section" (Glass 1985).

"The dedication of Hanover Bluff into the Illinois Nature Preserve System will protect an important natural area of the Wisconsin Driftless Division. To date, there are no nature preserves representing this natural division…The very high quality sand and dry dolomite hill prairies found here are the largest remaining prairies of this type in the natural division. The Inventory recognized only these sand hill prairies of Hanover Bluff" (Nÿboer 1986).

The Illinois Natural Areas Plan has driven state policy for 22 years in the areas of inventory, acquisition, protection, and stewardship. The Plan was the fundamental tool that paved the way for the passage of the Natural Areas Acquisition and Stewardship Act in 1984. This fund provides about $9 million per year for the acquisition and stewardship of natural areas; these funds are administered by the Division of Natural Heritage.

Since the late 1970s and continuing to the present, the system that was established in Illinois has been of enormous use and significance in preserving the small percentage of natural areas remaining in the states. It is important to note that merely placing a site on the Illinois Natural Areas Inventory does not protect the site – it merely recognizes that the site has significant natural features. Legal protection only occurs when a site is officially dedicated as an Illinois Nature Preserve (see below). However, inclusion of a site on the Inventory often does have influence within state agencies and other governmental bodies.

Ideally, all sites on the Natural Areas Inventory someday would be dedicated as Nature Preserves. However, some property owners find permanent legal jurisdiction over their land to be too restrictive at the present time. Also, dedication as a Nature Preserve usually precludes use of the land for some other activities, such as hunting and most recreational activities other than hiking. Some property owners find these limitations too restrictive and not compatible with current land usage. For these situations, two programs ancillary to the INPC system have subsequently been developed: 1) Natural Heritage Landmarks and 2) Land and Water Reserves. The Natural Heritage Landmark program encourages property owners to voluntarily protect and manage sites as natural areas; some of these are subsequently dedicated as official Nature Preserves. The owner signs an agreement and receives a certificate; however, the agreement can be terminated at any time with 30 days notice. The Land and Water Reserve program is relatively new and provides legal protection to natural areas, either permanently or for a specified number of years. Some kinds of activities not compatible with official Nature Preserve, such as hunting and fishing, are permitted within Land and Water Reserves. The Nature Preserves Commission must give approval for each new Land and Water Reserve. Currently there are 54 Land and Water Reserves totaling 21,469 acres in 36 counties.

Data from the Illinois Natural Areas Inventory is often used in combination with other information. At the time of European settlement, the landcover of Illinois was about 60% prairie and 40% forest. These figures come from Anderson (1970), who produced a map based on the original Government Land Office surveys. These surveys began in 1805 and were not completed until 1856 (McClain 2000). Iverson et al. (1989) took Anderson’s map and used Geographic Information System software to calculate the acreages of forest, prairie and open water in each county in Illinois. It was then possible to compare by county the original amount of forest and prairie and then to compare this with the results of the INAI. Figure 4 shows a map with the figures for prairie. The figures for the Grand Prairie Natural Division in east central Illinois are particularly shocking.


"If we could first know where we are and whither we are tending, we could better judge what we do and how to do it…." – Abraham Lincoln. Although this statement is quoted here far removed from its original context, it can be used to reflect Illinois’ position with regard to its natural resources by the early 1990s. The INAI and other programs discussed above provide considerable detail about a very limited aspect of Illinois, natural areas and endangered species. Yet, 90% of the land of Illinois is privately owned, and about 78% of the land is in agriculture (Bonfert 1995).

It is in this context that a number of projects commenced during the 1990s. Today these fall under Conservation 2000, a six year $100 million initiative designed to take a holistic, long-term approach to protecting and managing the natural resources of Illinois. Conservation 2000 funds nine programs across three state agencies. The web site for Conservation 2000 is <>.

Critical Trends Assessment Program

I am going to describe one key component, the Critical Trends Assessment Program (CTAP) and allied programs. The first stage of CTAP (CTAP-I) was initiated in 1991 and resulted in a seven volume, 1300 page technical report that was completed in 1994 . Volume 3, Ecological Resources (Illinois Department of Natural Resources 1994), summarized what was known about prairies, forest, wetlands, lakes and impoundments, and flowing waters. It became clear that despite the voluminous amount of information, there was not enough data to assess long-term trends of the environment in Illinois. This report served as a baseline on which to build a new stage of data collection and analysis.

This led to the development of the second stage of CTAP, CTAP-II. (Bailey et al. 2001, Bonfert 2000, Jeffords 2000). This is a multi-faceted, ecosystem-based monitoring framework that establishes a statistically valid sample of major ecosystems. It assesses both the condition and the extent of forest, grassland, wetland, and stream ecosystems at a state-wide level. Below are brief descriptions of the major components of CTAP-II.

Land-cover mapping

To measure the extent of the current Illinois landscape, the Illinois Land Cover Database was developed using satellite remote sensing and a Geographic Information System (GIS). The database has categories for 23 land cover classes in the following major categories: forest, wetland, open water, urban areas, agricultural land, and barren and exposed land. Resolution is 28.5 x 28.5 meters (93.5 x 93.5 feet). From this database was produced the Landcover Map of Illinois, which is available as a printed map, on a CD-ROM, and on the World Wide Web <>. Another project is underway to map the presettlement vegetation of Illinois at the level of section (one square mile) using the original Government Land Surveys (see above).

Resource Rich Areas

To serve as a baseline information, a project was initiated to define Resource Rich Areas (RRA) in Illinois (Suloway, Joselyn, and Brown 1996). Using GIS software, areas were delineated by major watersheds that are large enough to operate at the ecosystem level, have the potential for protecting or restoring habitat on a large scale, and contain examples of high quality natural communities that show significant habitat and species diversity (Jeffords 2000). Thirty Resource Rich Areas were identified, which cover 19.8% of the state but include 76% of the acres on the INAI and 55% of the INAI sites in the state.

Ecosystem Partnerships

These Resource Rich Areas served as the basis, later modified, for the development of Ecosystem Partnerships, which are public/private coalitions that combine natural resource stewardship with compatible economic and recreational development. Funding comes from Conservation 2000. To assist with Ecosystem Partnerships, technical and popular reports are prepared by scientists at the Illinois Natural History Survey, Illinois State Geological Survey, Illinois State Water Survey, and Illinois State Museum. For the standpoint of vegetation, these reports contain lists of all areas on the INAI and of nature preserves, descriptions of all natural communities, and a species list of vascular plants known from the partnership with the natural communities given for each species. The website for Ecosystem Partnerships is <>.


Vital to the overall goal of assessing critical long-term ecological trends in the state is the detailed monitoring program that has been established. Each year, four major categories are sampled: streams, forests, grasslands, and wetlands. There are two basic components of this program, one utilizing professional scientists and the other with volunteers.

Each year, five professional scientists (two botanists, an ornithologist, an entomologist, and an ichthyologist) sample 30 sites of each of the major categories that are randomly selected across the state. The sites selected do not need to be of Grades A and B under the guidelines of the INAI, but they must meet basic criteria. For example, forests are unacceptable that have been grazed so heavily that the shrub and herbaceous layers have been destroyed. There is a five-year cycle of monitoring, so that there are a total of 150 sites of each category, for a total of 600. Quantitative sampling methods are used and include a series of 0.25m2 quadrats along randomly placed transects; other methods are also used, depending on the ecosystem. Data collected for vegetation include species richness and dominance, percent cover, and Floristic Quality Index (Taft et al. 1997, Wilhelm and Masters 1999).

The volunteer program is called the EcoWatch Network, and it has six subprograms: RiverWatch, ForestWatch, PrairieWatch, WetlandWatch, SoilWatch, and UrbanWatch (Barber, Curtiss, and Niven 2000). The first began in 1995, the second in 1996, the third in 1999, and the others are under development. The volunteers take part in a training program to become "citizen scientists;" between 1995 and 1998, more than 2,000 individuals have participated in the program. Data collected by the volunteers is a subset of the professional’s procedures, but with less taxonomic resolution at both random and nonrandom locations. Volunteers include high school teachers, their students, and interested adults. While the main goal of EcoWatch is to gather scientifically valid data that are helpful in long-term monitoring, the use of volunteers also builds an environmentally conscious constituency. The website for EcoWatch is <>.


At the end of the 18th century, Illinois was a natural wilderness with original forests, myriad types of prairies, functional wetlands, and pristine lands and streams. At the end of the 19th century, most of the landscape had been converted to agriculture and urban development. However there had been numerous studies conducted on the vegetation of Illinois. At the end of the 20th century, very little of the natural landscape remained. Yet much progress was made in preserving what was left through the framework developed by the Natural Land Institute, Illinois Nature Preserves Commission, the Illinois Natural Areas Inventory, the Endangered Species Protection Board, and the Division of Natural Heritage. However, it was obvious that even with all that had been done, we did not have the kinds of information to assess long term trends of the environment of Illinois. The Critical Trends Assessment Program was established to close this gap. Prospects for the 21st century regarding the preservation of the natural environment of Illinois look as good as can be expected considering how little of our natural landscape is still extant. We have the means to protect natural areas and endangered species, and we are gaining the knowledge to plan intelligently for the future. Already, the natural resource information and GIS capability that began with plants have contributed to the very broad range of planning decisions with positive effects on health and economy as well as environment. Continuing recognition of the broad scale of benefits of analysis of natural resource data has aided in continued strong funding support. The ultimate success or failure depends largely on how successful we are in conveying information to policy makers, managers, and the citizenry of Illinois. The stewardship, volunteer, and partnership programs have provided a strong start is this essential direction.


I would like to thank the following for their invaluable assistance in the preparation of this paper: J. B. Phipps for organizing this symposium and inviting my participation; Francis M. Harty, Illinois Department of Natural Resources, for helping sort out critical events that occurred in the 1970s and 1980s; Sue Merchant, Natural Land Institute, for providing information about George Fell; Kate Hunter, Illinois Natural History Survey, for generating Figures 2 and 3 and for extracting other information; Adrienne L. Edwards and Geoffrey A. Levin, Illinois Natural History Survey, for critically reading the manuscript; and Paul M. Catling, Agriculture and Agri-Food Canada, for the final editing of the manuscript. Figures 2 and 3 utilized data from the Illinois Natural Heritage Database, maintained by the Division of Natural Heritage, Illinois Department of Natural Resources, and were made using the facilities of the Geographic Information System unit at the Illinois Natural History Survey.

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Mohlenbrock, R. H. and D. M. Ladd. 1978. Distribution of Illinois vascular plants. Southern Illinois University Press, Carbondale and Edwardsville. 282 pages.

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Post, S. L. 1991. Appendix One: Native Illinois species and related bibliography. Pages 463—475 in L. M. Page and M. R. Jeffords, editors. Our living heritage: The biological resources of Illinois. Illinois Natural History Survey Bulletin 34(4).

Risser, P. G. 1984. Bibliography of Illinois Vegetation. Illinois Natural History Survey Biological Notes No. 121. 51 pages.

Robertson, K. R., R. C. Anderson, and M. W. Schwartz. 1997. The tallgrass prairie mosaic. Pages 55—87 in M. W. Schwartz, editor, Conservation in Chronically Fragmented Landscapes. Chapman and Hall, New York.

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Schwegman, J. 1973. Comprehensive plan for the Illinois Nature Preserves System. Part 2. The natural divisions of Illinois. Illinois Nature Preserves Commission, Rockford. 32 p. + map.

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Van Zandt, N. B. 1818. A full description of the soils, water, timber, and prairies of each lot or quarter section of the military lands between the Mississippi and Illinois rivers. P. Force, Washington City. 121 pages.

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White, J. 1981b. Grading natural quality of a natural community. Pages 371—373 in A. E. Radford, D. K. S. Otte, L. J. Otte, J. R. Massey, and P. D. Whitson, Natural Heritage Classification, Inventory, and Information. University of North Carolina Press, Chapel Hill.

White, J. 1981c. Some procedures for detecting disturbances. Pages 374—379 in A. E. Radford, D. K. S. Otte, L. J. Otte, J. R. Massey, and P. D. Whitson, Natural Heritage Classification, Inventory, and Information. University of North Carolina Press, Chapel Hill.

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Willman, H. B. and J. C. Frye. 1970. Pleistocene Stratigraphy of Illinois. Illinois State Geological Survey Bulletin 94, 204 pages.

Winterringer, G. S. and R. A. Evers. 1960. New records for Illinois vascular plants. Illinois State Museum Scientific Papers Series Vol. XI. 135 pages.

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Updated: 9 September 2002